1. Field of the Invention
The present invention relates to a communication apparatus having a control function of controlling power consumption and an electric power control method.
2. Description of the Related Art
It is common practice to build a LAN for sharing information and for effective use of an apparatus such as a printer for printing, in a case that a system including a plurality of computers is built. In recent years, a wireless LAN is used for such system. The wireless LAN is expected to be used more frequently in the future since it does not necessitate a LAN cable, and the convenience of a portable information processing apparatus such as a notebook PC can be effectively taken advantage of. As such wireless LAN, two types of networks are known. One is an infrastructure network which allows communication via a master station called an access point, and the other is an ad hoc network which allows communication between wireless terminals without an access point.
Conventionally, since many wireless terminals used in the wireless LAN are portable, a battery is used for a power supply. This causes a big problem associated with control of power consumption. In U.S. Pat. No. 5,943,610 (Japanese Patent Laid-Open No. 9-275373), a technique for executing electric power control on the basis of instructions from a master station is disclosed as a method for controlling transmission power in a wireless terminal. Japanese Patent Laid-Open No. 2003-347943 discloses a technique for controlling transmission power in a wireless terminal on the basis of the remaining battery level of a battery in the wireless terminal. Furthermore, Japanese Patent Laid-Open No. 8-88579 discloses a technique for controlling transmission power in a wireless terminal in accordance with the reception level of a signal from a communication partner, in a case that the wireless terminal is set in the power saving mode.
It was difficult to apply the conventional transmission power control based on instructions from a master station to an ad hoc network having no master station. If autonomous transmission power control in which each wireless terminal controls electric power by itself is applied to an ad hoc network, each wireless terminal controls transmission power independently. Therefore, transmission power of each wireless terminal can be excessively large or small. As a result, power consumption increases, or communication fails.